1. Field of the Invention
The present invention relates to an insulating film, more specifically, to an insulating film having an adequately uniform thickness and moreover, excellent in dielectric properties as an interlayer insulating film material in semiconductor devices and the like.
2. Description of the Related Art
A silica (SiO2) film formed by a vacuum process such as chemical vapor deposition (CVD) has hitherto been used frequently as an interlayer insulating film for semiconductor devices and the like. With a purpose of forming a more uniform interlayer insulating film, an insulating film of an application type composed mainly of a hydrolysate of a tetraalkoxysilane, which is called SOG (Spin on Glass) film, has recently been used. With an increase in the integration density of a semiconductor device or the like, a low-dielectric-constant interlayer insulating film composed mainly of a polyorganosiloxane which is called organic SOG is under development. In particular, a siloxane compound having a cyclic structure can have a reduced dielectric constant because owing to its bulky cyclic structure, it has free spaces around the molecular chain thereof.
It is however confirmed by the Raman analysis that the cyclic structure of the cyclic polysiloxane compound is broken during a curing step. As a result of the breakage of the cyclic structure, a film obtained using such a compound inevitably has a high dielectric constant.